Stiffener material for shoes and method of making



Sept. 15, 1954 s. .M. GRISWOLD 3, 2

sum-"sum MATERIAL FOR SHOES AND METHOD OF MAKING Filed March 2, 1962 H m Z By his Attorney 019% t Q .Nr Q wk NA g .l t w MN United States Patent 3,149,022 STIFFENER MATERIAL FGR SHOES AND METHOD OF MAKENG Stanley M. Griswold, Newton, Mass, assignor to United Shoe Machinery Corporation, Boston, Mass, :1 corporation of New Jersey Filed Mar. 2, 1952, Ser. No. 177,072 9 (Zlaims. (Cl. 162-108) This invention relates to improvements in laminated solvent-activatable sheet stiffener material, particularly material for stiffening end portions of shoes and to a method of making such material.

In my copending application for United States Letters Patent, Serial No. 847,550, filed October 20, 1959, now Patent No. 3,102,836, there is disclosed a solvent-activatable sheet stiffener material comprising a water-laid layer of intermixed fibers and coalescible particles of a stiffening agent soluble at room temperature in an organic solvent. The layer is formed by draining a furnish of fibers containing stiffening agent particles dispersed therein through a thin, relatively open fibrous sheet to which the layer becomes attached by interspersion of fibers. This composite sheet material is effective for its intended purposes and is low in cost.

in my further copending application for United States Letters Patent, Serial No. 95,423, filed March 13, 1961, now Patent No. 3,102,837, there is disclosed an improvement over the first mentioned application involving the deposition of a binder to prevent displacement of stiffener particles from surface portions of the stiffener material. This improvement is effected by treating the surface of the layer of fibers and particles after formation and while still wet, with an aqueous dispersion of a binder to impregnate the web to a depth of a substantial portion of its thickness. The deposited binder provides a marked improvement in the ability of the stiffener sheet material to be skived through holding the particles of stiffening agent against displacement by the skiving blade. Also the binder improves tl e tackiness of the surface of the fibrous layer when the material is activated by solvent.

Some difficulty has been found with separation of the faoric layer from the layer of fibers and stiffener particles when the sheet is died out into stiffener blanks, particularly where the fabric is a relatively strong re-enforcing material.

it is an object of the present invention to provide a stiffener sheet material in which the union between a reenforcing fabric and a layer of fibers and stiffener particles formed thereon is reinforced to provide increased strength to resist separation of the fabric and layer in the course of dieing out and skiving.

To this end and in accordance with a feature of the present invention, the bond between a fabric re-enforcement and a layer of fibers and stiffener particles formed on the fabric with fibers of the layer interspersed with fibers of the fabric is reinforced by depositing on and at the surface of the fabric and adjacent portions of the fiber and stiffener particle layer a deposit of a thermoplastic resinous polymeric material and thereafter heating that surface to fuse the deposited resin to form an organic solvent permeable pellicle and to cause the resin to reinforce the union between fabric and layer and hold the fabric firmly to the fibrous layer.

Other features and advantages of the invention will be understood more fully from the following detailed description taken in connection with the accompanying drawings in which:

FIG. 1 is a diagrammatic View with some parts enlarged and other parts broken away for purposes of clarity of an arrangement for making the stiffener material of the present invention; and

3,149,ZZ Patented Sept. 15, 1964 FIG. 2 is an enlarged sectional view of the stiffener material of the present invention.

Referring to FIGS. 1 and 2, the sheet material of the present invention comprises a water-laid layer 10 of fibers in which is incorporated coalescible discrete particles of a plastic such as an organic solvent soluble stiffening agent and a reinforcing fabric sheet 12. The layer 10 is formed by filtration from a suitable furnish through the sheet 12 of relatively open, fibrous fabric so that fibers of the layer 10 and the sheet 12 are interspersed at the interface 14 (FIG. 2). Organic solvent soluble resinous binder material may be deposited on the fibers and particles in a portion 16 of the layer 10 from the surface of the layer it? opposite the sheet 12 depthwise into the layer a substantial portion of the entire thickness of the layer, e.g. about one-third of the thickness.

The fiber content of the layer 10 may comprise any suitable papermaking fibers or mixture of fibers such as cotton, nylon, jute, hemp, hair, wool, kraft or sulfite pulp or asbestos. I have found that kraft paper pulp fibers have adequate strength and form a very satisfactory product.

The coalescible plastic material used in a sheet material intended for shoe stiffening suitably comprises discrete particles of a normally solid, resilient, high molecular Weight material which does not melt below about C. and preferably about C., but is soluble at room temperature in a volatile organic solvent. These plastics include, for example, organic solvent soluble resinous polymers and copolymers of ethylenically unsaturated monomers such as the monovinyl aromatic hydrocarbons of the benzene series including polystyrene and polyvinyl toluene, polyvinyl acetate and the acrylate and methacrylate polymers. Cellulose derivatives, such as cellulose acetate, natural resins, such as modified rosin and the like may also be used alone or in combination.

The furnish 18 is an aqueous dispersion and ordinarily the plastic particles will be selected from largely or entirely water-insoluble materials. However, it is also possible to introduce additives to the furnish which reduce the solubility of desirable plastics possessing some solu bility in water.

The particles of plastic may be produced by pulverizing scrap plastic material, for example, the scrap resulting from the manufacture of polystyrene lenses which is now commonly available. Many plastic materials including polystyrene and polyvinyl toluene may also be employed in the form of small beads made by known suspension polymerization techniques. Particulate material, e.g. polystyrene beads of which substantially all passes a #100 mesh sieve, and up to about 25% passes a #300 mesh sieve has been found satisfactory. The sieve num bers refer to U.S. Standard Sieves.

The proportion of plastic particles to fiber may be varied considerably, but for most purposes I find that at least an equal weight is needed and a ratio in the range of about 2 to about 5 parts by weight of plastic particles to one part of fiber is most suitable.

In making a sheet according to one form of the present invention, the plastic particles and fiber are beaten up with a suitable quantity of Water to form an aqueous dispersion of furnish which is supplied to the vat 17 of a cylinder type paper-making machine 19. The furnish is strained through a sheet 12 of relatively open fibrous fabric disposed on a support, usually a wire screen cyl inder 20 as in the machine 19. In fact, the support for the facing sheet may be in any form which provides suitable backing for the sheet 12 while permitting filtration through the fibrous fabric sheet.

The fabric sheet 12 should comprise fibers in relatively free relation, e.g. unsized for effective coaction with the fibers of the furnish to allow interspersion. The sheet should be relatively open and flexible, and should have substantial strength. The open character of the sheet is important to permit drainage of the water of the furnish while holding back the fiber and plastic particles. Also openings in the sheet permit some penetration of fibers of the water-laid fibrous layer into the fabric as well as interpersion of fibers of the layer and fibers of the fabric to provide a mechanical union between the fabric and the fibrous layer to enable handling of the composite sheet. Preferred fabric sheets are open-mesh materials such as cheese cloth, tobacco cloth or Osnaburg. These fabrics come in a number of weights and thicknesses ranging from about 2 to about 5 ounces per square yard and from about to about mils in thickness. Non-woven fabrics may also be used but appear to be less satisfactory.

After sheeting out the furnish to form a layer of desired thickness, water may be removed mechanically from the sheet to reduce the amount which must later be evaporated. Removal of water may be effected by suction and/ or by squeezing the sheet as between rolls 22. While the composite sheet is still wet, an aqueous dispersion of a binder may be applied preferably by a reverse rotating coating roll 24 with its lower portion in binder in trough 26 to the surface of the sheet opposite the surface on which the fabric 12 is secured. It appears that the water content of the sheet holds the fibers in a more extended relation than would be the case in a dry sheet and also the water eliminates difficulties caused by dry sheets, particularly difficulties of penetration of the binder dispersion into the fiber layer.

The binder may be any liquid solution or dispersion of a material capable of forming a coherent deposit to hold the fibers and particles together. But it is preferred to use a binder which will have certain rubbery characteristics for more effective improvement of the hand of the sheet, i.e. will have the ability to hold the fibers and particles together even where the sheet is subjected to limited flexing. Likewise, it is desirable that the binder be capable of at least partial solution or swelling to a tacky condition when the stiffener is activated by organic solvent. A rubbery copolymer of styrene and butadiene containing from about to 50% of butadiene is a desirable component of the binder and is readily commercially available as a latex, i.e. an aqueous dispersion. It is found that the ability to develop surface tack, and the effectiveness of the binder as an aid both in improving the character of the stiffener sheet before activation and in increasing strength and stifiness after activation are improved through the incorporation with the rubbery copolymer latex of a substantial proportion of a latex of a high styrene content butadiene-styrene copolymer, i.e., a copolymer in which the styrene content may be from 50 to 95%. Suitable mixtures of the latices may comprise .from about 30% to about 90% by weight solids of the rubbery copolymer with about 10% to 70% by weight solids of the high styrene content copolymer. Latex compositions having a solids content of from about 5% to 15% have been found useful for impregnating a fiber and plastic particle layer according to the present invention. Effective impregnation to achieve the desired results has involved applying from about 0.2 to about 2 ounces of the copolymer solids per square yard of the layer. This impregnation will penetrate up to about onethird of the thickness of the layer. After this impregnation, the sheet is almost completely dried by passing around heated rolls 28 and preferably is given a surface coating by being passed while still hot. from drying rolls 28 over roll 30 with its lower portion immersed in a liquid coating composition in trough 32. This coating composition may be a rubbery copolymer latex of a high styrene content butadiene styrene copolymer in which the styrene content may be from 50 to 95%. The coating is dried by passing the coating material around drying rolls 34.

Thereafter the dried material is treated in accordance with the present invention to form an organic solventpermeable pellicle on the fabric surface. To form the pellicle the dried sheet may be passed beneath one or more coating devices shown as troughs 36 carrying an aqueous resin and/ or rubbery polymer or copolymer latex or latices and then beneath a doctor blade 40. ferred to apply the latex material in two stages using a latex composition capable of limited penetration in the first stage and a less penetrating composition of material readily softenable by organic solvent to a tacky condition in the second stage. In the two stage treatment, the first applied latex is applied in amount which penetrates from 0.005" to 0.015" but not over one-half and preferably not over about one-third of the thickness into the fiber layer with portions remaining on the surface in the opening between the threads of the fabric. The second applied latex remains on the surface of the fabric fibers and in the openings between the threads of the fabric. The coated surface is next dried by passing through a drying tunnel 42 and is then subjected to heating to fuse the deposited thermoplastic material. Radiant heat, suitably from infra-red heat source 44 is the preferred type of heating since it is effective to fuse the deposited material on the surface without extensive softening and fusion of the resinous stiffener material within the fibrous layer. Other forms of applying heat to the coated surface may be employed as for example, a stream of heated gas or a fiame. Heating by contact with a hot surface is unsatisfactory since the fused material transfers to and builds up on the hot surface. Fusion by heating in a conventional oven has not been satisfactory since the entire sheet becomes hot, the interior resin particles softened and the ultimate product is too stiff for use after cooling.

Thermoplastic materials for coating the fabric include one or more resinous and/ or rubbery aqueous latices such as a polystyrene latex or an emulsion copolymer latex of butadiene and styrene comprising 50 to styrene desirably in combination with a polystyrene latex. Latex compositions having a solids content of from about 5% to about 50% are preferred. A preferred combination giving excellent holding action of the fabric to the fibrous layer as well as excellent tack when the sheet is activated by solvent and assembled in the shoe involves depositing from the first trough 36 a latex mixture compounded to give limited penetration into the fibrous layer and a mixture of a copolymer latex and polystyrene latex with superior ability to develop tack and adhesion after solvent activation from the second trough 36.

The fusion of the deposited material requires that there be developed a temperature sufliciently above the melting point of the deposited material so that the material may flow into wetting engagement with the fibers of the fabric and of the layer of fibers and stiffener particles to reinforce the union between the fabric and the layer of fibers and particles. With the above mixture of polymer and copolymer materials, a temperature of about 275 to 350 F. fuses the deposited material to an organic solvent permeable pellicle which is practically impervious to liquid water.

Apparatus useful for supporting the fabric 12 for straining a furnish 18 to form a felted fibrous sheet 10, may comprise the modified cylinder-type paper-making machine 19 diagrammatically illustrated in FIG. 1. As there shown, the machine 19 comprises the vat 17 to which the furnish 18 is supplied. Cylinder 20 is rotatably mounted in the vat l7 and is provided with means for driving it (not shown). A pipe 50 for withdrawing liquid is disposed in the interior of the cylinder 20. The cylinder 20 differs from conventional papermaking cylinders in that the screen'is of substantially larger mesh. It is desirable that the openings in the screen be at least about /a greater than the dimension of the largest plastic or resin particles of the furnish to prevent plugging of the screen by the particles. It should be noted that the screen openings It is pre 0 may in some instances be somewhat reduced by reinforcing wires and the screen opening size referred to is the actual screen opening. Depending on the size of the plastic particles, there may be used screens from size No. 12 to size No. 30 (U.S. Bureau of Standards, Standard Screen Series, 1919).

For the first operation to form a mechanically linked composite sheet of fabric and water-laid fiber-plastic particle layer 10, fabric 12 is passed around a roller 52 which lays it down on the screen cylinder and the fabric 12 is carried around by rotation of the cylinder. The water component of the furnish passes through the fabric 12 to the interior of the cylinder 20 leaving behind on the fabric a layer 10 of intermixed fibers and plastic particles. Fibers from the furnish 18 deposited on the fabric 12. penetrate and become entangled with, i.e. intersperse the fibers of the fabric 12 to attach mechanically the deposited intermixture of fibers and plastic particles to the fabric 12. When the fabric 12 and the attached layer 1%) of fibers and plastic particles have passed nearly around the cylinder 20, they are lifted from the surface of the cylinder by a couch roll 56 and felt 58 and carried up with the felt over the roller 62;. From the roller 62., the composite of the fabric 12 and felted layer 10 is passed between squeeze rolls 22 which mechanically express a portion of the water content and then passes over a coating roll 24 of which the lower portion dips into a body 64 of binder liquid in the trough as. The roll 24 rotates in a direction so that its surface is moving counter to the direction of movement of the composite sheet so that substantially the entire quantity of binder liquid picked up by the surface of the roll 24 is transferred and serves to impregnate the fiber layer 10.

After the step of impregnation, the sheet is dried by suitable drying means such as heated drying rollers 28 and is then passed with the fiber layer 10 in engagement with a second coating roll 30 rotating in the direction of movement of the composite sheet, but at a higher surface speed. The lower portion of the roll 30 is immersed in a trough 32 containing an emulsion of thermoplastic resinous material. Material picked up by the surface of the roll is deposited on the surface of the fiber layer 10. The sheet is further dried by passing around heated rolls 34.

The dried sheet is then passed beneath successive coat ing troughs 36. The first trough may contain a mixture of a polystyrene latex and a high styrene butadiene rubbery copolymer latex, suitably a copolymer of about equal parts by weight of styrene and butadiene. Ordinarily these latices are combined using an excess of the polystyrene latex and a useful mixture uses the proportions of about 9:1 based on the weight of solids in the latices. The latex composition is adjusted as to viscosity, wetting agent, solids content and so on to coat the fabric and portions of the fiber layer between the threads of the fabric, with limited penetration into the fiber layer itself. The mixed latex is applied in quantity to provide from about 1 to about 4, preferably about 2 ounce solids per square yard of the sheet.

The second trough 36 desirably contains a mixture of about 3 parts by weight solids of the preceding high styrene butadiene rubbery copolymer latex and about one part by weight solids of a polystyrene latex. This coat is applied in quantity to give from about A to about 1 ounce, preferably about ounce solids per square yard of the sheet. The doctor blade 40 following the coating troughs removes excess coating and insures that the coating is spread uniformly and-reaches all surface portions of the sheet. Preferably the quantity of latex applied from the two troughs is controlled so that the ratio of polystyrene solids to copolymer solids in the double coating is from about 3:1 to about 10:1.

Following the application of the coating material the sheet is dried for example, a drying tunnel 42 to remove substantially all of the water. The dried sheet is then passed beneath a source of radiant heat such as infra-red lamps 44 to fuse the polymeric material cleposited on the fabric. Although applicant does not wish to be bound by the following, it appears that the material from the first trough 36, comprising a relatively high proportion of polystyrene is particularly effective in reinforcing the union between the fiber layer and fabric 12 and that the second applied material which does not enter so intimately into the sheet is particularly effective to provide tack and adhesion when the stiffener material is activated by solvent in use of the stifiener. In the quantities used, even though the coatings are fused, the pellicle is sufiiciently open or porous so that it does not interfere with penetration of the surface by a solvent activator.

Following the fusion of the coating material, the sheet is cooled and may be pressed to smooth the surface but is not pressed to an extent markedly to densify the fiber layer. The pressing is ordinarily controlled to give a compactness of the fiber layer such that on simply dipping a piece of the material in solvent and weighing promptly, the pickup is from about 50% to about 65% by Weight of the sample. The sheet may be cut into stiffener blanks or stored for use in sheet form.

The following example is given to aid in understanding the invention, but it is to be understood that the invention is not restricted to the particular materials, purposes or procedures set forth in the example.

Example.A furnish was prepared by beating kraft pulp in water using a Hollander type beater device. The furnish was adjusted to a fiber content of 0.14% fiber and there was then introduced polystyrene beads of which almost all pass through a No. 100 screen (screen opening 0.006), and about 25% pass through a No. 300 screen (screen opening .0019") in amount to bring the resin content of the furnish to 0.35%

Osnaburg cloth was drawn from a roll and laid down on the screen of a cylinder type papermaldng machine by a roll resting on the screen at the top of the cylinder. The screen was No. 14 (screen opening 0.0555"). The cloth was brought around the cylinder and around a couch roll and felt at the top of the cylinder.

The cylinder which was 18 inches in diameter was set in rotation at about 3 r.p.m. and furnish introduced to fill the vat of the machine nearly to within 2 inches of the top of the cylinder. The white water from the furnish strained through the cloth on the cylinder screen leaving behind a layer of intermixed fiber and resin. The liquid entering the interior of the cylinder was withdrawn. The layer of intermixed fiber and resin particles increased in thickness as it passed around the cylinder and was lifted oil the screen as a composite sheet by the couch roll and felt. The composite sheet was passed between rolls to squeeze water from it. In the sheet, the fibers of the intermixed fiber and resin particle layer were interspersed with the fibers of the cloth to an extent sufficient to hold the fiber and resin particle layer firmly to the cloth.

A polystyrene latex and a latex of a copolymer styrene and 20% butadiene were mixed inproportions to give a ratio based on the solids of 1 part of polystyrene to 4 parts of the copolymer and the mixture diluted to 15% by weight solids. The mixture was supplied to the tray into which a coating roll dipped. The composite sheet of intermixed fiber and resin particle layer and cloth was passed over the coating roll with the fiber and resin particle layer against the roll. The roll rotated in the direction of movement of the composite sheet and the surface of the roll picked up the mixed latex composition from the tray and deposited it on the surface of the layer. The speed of the roller was controlled to provide a deposit of about 0.2 ounce of solids of the latex per square yard of the composite sheet. The sheet was then dried by passing it around heated drying rollers.

The sheet then passed to a second coating roll to apply a further coating of mixed polymer and copolymer latices which remain largely on the surface. The coated sheet was dried on heated drying rollers. The total solids of the two coatings was about /2 ounce per square yard.

After drying, the fabric surface of the composite sheet was coated first with about 2 ounces solids per square yard of a mixture of a latex of a copolymer of equal parts of butadiene and styrene and a polystyrene latex in the ratio by weight of solids of the two latices of about 1:9. The mixed latices penetrated into the fiber layer to a distance of about .005 inch. The surface was then coated with about /2 ounce solids per square yard of a mixture of a latex of a copolymer of 80 parts of styrene to 20 parts of butadiene and a polystyrene latex in the ratio by Weights of solids of the two latices of about 3:1. The sheet was then passed through a drying tunnel heated with steam pipes carrying steam at 100 pounds pressure to dry the coating. When the sheet was dried it was passed beneath infra-red heaters to fuse the deposited polymeric material. The surface temperature reached in this heating step was about 250 to 300 F. The sheet was then cooled and lightly pressed to densify it to a stage such that when dipped in a solvent comprising regular naptha and toluol in the ratio by volume of about 3:2, a portion of the sheet would pick up 55% by weight of solvent based on the dry weight of the portion. The sheet material was cut into blanks having an outline shape for insertion between the layers at the toe of a shoe. These blanks were dipped in the solvent mixture referred to above and after dipping had a softness well adapted for insertion in the layers at the toe of a shoe and had tacky surfaces adapted to form bonds with ad jacent layers of the shoe. After insertion of the stiffener blanks in shoes, lasting and standing overnight, the shoe toes were found after removal of the last to be strong, stiff and resilient and to preserve faithfully the shape of the last under the conditions encountered in use of the shoe.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a hardenable sheet material for stiffening end portions of shoes comprising a porous water-laid fiber layer with coalescible discrete particles of a normally solid, Water-insoluble, organic solvent soluble, heat softenable stiffening agent distributed through the layer, the weight of the particles being from 1 to 5 times the weight of the fibers, a thin relatively open fibrous fabric with fibers of said layer interspersed with fibers of said fabric to hold said layer in associated relation, the improvement comprising a fused organic solvent permeable pelhole of an organic solvent soluble polymeric thermoplastic material on the fabric and extending into said layer to an extend less than one-half the thickness of said layer reinforcing the union between said fabric and said layer.

2. In a hardenable sheet material for stiffening end portions of shoes comprising a porous water-laid fiber layer with coalescible discrete particles of a normally solid, water-insoluble, organic solvent soluble, heat softenable stiffening agent distributed through the layer, the weight of the particles being from 1 to 5 times the weight of the fibers, a thin relatively open fibrous fabric with fibers of said layer interspersed with fibers of said fabric to hold layer and fabric in associated relation, the improvement comprising a fused organic solvent permeable pellicle of a polymeric thermoplastic material on the fabric and extending into said layer to an extent less than one half the thickness of said layer reinforcing the union between said fabric and said layer, said pellicle comprising a copolymer of from about 50% to about 95% styrene and from about 50% to about 5% butadiene and polystyrene resin.

3. In a hardenable sheet material for stiffening end portions of shoes comprising a porous water-laid fiber layer with coalescible discrete particles of a normally solid, water-insoluble, organic solvent soluble plastic distributed through the layer, said particles being present in the ratio of about 1 to 5 parts by weight to 1 part by weight of the fibers and said particles being of a size distribution as determined with US. Standard Sieves in which substantially all will pass a No. 100 mesh sieve and up to about 25% will pass a No. 300 mesh sieve, a thin relatively open fibrous fabric with fibers of said layer interspersed with fibers of said fabric to hold said layer and fabric in associated relation, the improvement comprising a fused organic solvent permeable pellicle of a polymeric thermoplastic material on the fabric and portions of the surface of said layer intermediate the fibers of said fabric reinforcing the union between said fabric and said layer, the polymeric material of said pellicle extending into said layer from about 0.005 inch to about 0.015 inch, but not over one-half the thickness of said layer, said pellicle comprising a copolymer of from about 50% to about styrene and from about 50% to about 5% butadiene and polystyrene resin in a ratio of from about 1:3 to about 1:10 by weight.

4. In a hardenable sheet material for stiffening end portions of shoes comprising a porous water-laid fiber layer with coalescible discrete particles of a normally solid, water-insoluble, organic solvent soluble plastic distributed through the layer, said particles being present in the ratio of about 1 to 5 parts by weight to 1 part by weight of the fibers and said particles being of a size distribution as determined with US. Standard Sieves in which substantially all will pass a No. mesh sieve and up to about 25% will pass a No. 300 mesh sieve, a thin relatively open fibrous fabric with fibers of said layer interspersed with fibers of said fabric to hold said layer and fabric in associated relation, the improvement comprising a fused organic solvent permeable pellicle of a polymeric thermoplastic material on the fabric and portions of the surface of said layer intermediate the fibers of said fabric reinforcing the union between said fabric and said layer, the polymeric material of said pellicle penetrating said layer from about 0.005 inch to about 0.015 inch, but not over one-half the thickness of said layer, said pellicle comprising a copolymer of from about 50% to about 95% styrene and from about 50% to about 5% butadiene and polystyrene resin in a ratio of from about 1:3 to about 1:10 by Weight of solids and said pellicle providing a weight of polymer of from about 1% to about 5 ounces per square yard.

5. In a hardenable sheet material for stiffening end portions of shoes comprising a porous Water-laid fiber layer with coalescible discrete particles of a normally solid, water-insoluble, organic solvent soluble plastic distributed through the layer, said particles being present in the ratio of about 2 to 5 parts by weight to 1 part by weight of the fibers and said particles being of a size distribution as determined with US. Standard Sieves in which substantially all will pass a No. 100 sieve and up to about 25% will pass a No. 300 mesh sieve, a thin relatively open fibrous fabric with fibers of said layer interspersed with fibers of said fabric to hold said layer and fabric in associated relation, the improvement comprising a fused organic solvent-permeable pellicle of a polymeric thermoplastic material on the fabric and portions of the surface of said layer intermediate the fibers of said fabric reinforcing the union between said fabric and said layer, said pellicle comprising an inner portion penetrating said layer from about 0.005 to about 0.015 inch, but not over about one-third of the thickness of said layer of a mixture of polystyrene resin and a copolymer of from about 50% to about 95% by weight styrene and from about 50% to about 5% butadiene in a ratio by weight of about 9:1, said inner portion providing from about 1 to about 4 ounces per square yard, and an exterior portion of said pellicle comprising a mixture of polystyrene resin and a copolymer of from about 50% to about 95% styrene and from about 50% to about 5% butadiene in a ratio of from about 1:3 and in amount to provide from about 4 to about 1 ounce per square yard.

6. In the method of making hardenable sheet material for stiffening end portions of shoes comprising the steps of forming a sheet by straining an aqueous dispersion of fibers and fine discrete particles of a normally solid, coalescible stiffening agent at least equal in Weight to the weight of the fibers through a thin relatively open fibrous fabric, said sheet comprising a layer of fibers with said particles distributed therethrough and with fibers of said layer interspersed with fibers of said fabric to hold said fabric and layer together as a sheet and removing a major proportion of the water content of said sheet, the improvement comprising coating the fabric-covered surface of said sheet with an aqueous latex of an organic solvent soluble thermoplastic material, said latex extending into said layer to an extent less than one-half the thickness of said layer, evaporating water from the applied coating and thereafter subjecting the dried coating on said fabric to radiant heat to fuse the deposited thermoplastic material to an organic solvent permeable pellicle reinforcing the union between said fabric and said fiber layer.

7. In the method making hardenable sheet material for stiffening end portions of shoes comprising the steps of forming a sheet by straining an aqueous dispersion of fibers and fine discrete particles of a normally solid, coalescible stiffening agent at least equal in weight to the weight of the fibers through a thin relatively open fibrous fabric, said sheet comprising a layer of fibers with said particles distributed therethrough and with fibers of said layer interspersed with fibers of said fabric to hold said fabric and layer together as a sheet and removing a major proportion of the water content of said sheet, the improvement comprising coating the fabric-covered surface of said sheet with an aqueous dispersion comprising polystyrene and a copolymer of from about 50% to 95% styrene and from about 50% to 5% butadiene, said dispersion extending into said layer to an extent less than onehalf the thickness of said layer, evaporating Water from the applied coating and thereafter subjecting the dried coating on said fabric to radiant heat to fuse the deposited copolymer and polystyrene to an organic solvent permeable pellicle reinforcing the union between said fabric and said fiber layer.

8. In the method of making hardenable sheet material for stiffening end portions of shoes comprising the steps of forming a sheet by straining an aqueous dispersion of fibers and fine discrete particles of a normally solid, coalescible stiffening agent, the weight of said particles being from about 1 to about 5 times the weight of the fibers, through a thin relatively open fibrous fabric, said sheet comprising a layer of fibers with said particles distributed therethrough and with fibers of said layer interspersed with fibers of said fabric to hold said fabric and layer together as a sheet and removing a major proportion of the water content of said sheet, the improvement comprising coating the fabric-covered surface of said sheet With an aqueous dispersion of a copolymer of from about 50% to about 95% styrene and from about 50% to about 5% butadiene and a polystyrene latex, said dispersion and latex extending into said layer to an extent less than onehalf the thickness of said layer, evaporating Water from the applied coating and thereafter subjecting the dried coating on said fabric to radiant heat to fuse the deposited copolymer and polystyrene to an organic solvent permeable pellicle reinforcing the union between said fabric and said layer, cooling said sheet and lightly pressing it to bring it to a density having a solvent pick up of from about 5 0% to about by weight based on the dry weight of the sheet.

9. In the method of making hardenable sheet material for stiffening end portions of shoes comprising the steps of forming a sheet by straining an aqueous dispersion of fibers and finediscrete particles of a normally solid, coalescible stiffening agent, the weight of said particles being from about 1 to about 5 times the Weight of the fibers through a thin relatively open fibrous fabric, said sheet comprising a layer of fibers with said particles distributed therethrough and with fibers of said layer interspersed with fibers of said fabric to hold said fabric and layer together as a sheet and removing a major proportion of the water content of said sheet, the improvement comprising coating the fabric-covered surface of said sheet With an aqueous dispersion of a latex of a copolymer of from about 50% to about styrene and from about 50% to about 5% butadiene and a polystyrene latex, said latices being controlled in quantity applied and penetrating ability to provide from about 1% ounce to about 5 ounce solids per square yard of sheet and to extend into said layer from 0.005 to 0.015 inch but not more than one-half the thickness of said layer, evaporating water from the applied coating and thereafter subjectingthe dried coating on said fabric to radiant heat to fuse the deposited copolymer and polystyrene to an organic solventpermeable pellicle reinforcing the union between said fabric and said layer, cooling said sheet and lightly pressing it to bring it to a density having a solvent pick up of from about 50% to about 65% by weight based on the dry weight of the sheet. 7

References Cited in the file of this patent UNITED STATES PATENTS 1,351,374 Growell Aug. 31, 1920 1,739,578 Clapp Dec. 17, 1929 2,358,204 Bird Sept. 12, 1944 

6. IN THE METHOD OF MAKING HARDENABLE SHEET MATERIAL FOR STIFFENING END PORTIONS OF SHOES COMPRISING THE STEPS OF FORMING A SHEET BY STRAINING AN AQUEOUS DISPERSION OF FIBERS AND FINE DISCRETE PARTICLES OF A NORMALLY SOLID, COALESCIBLE STIFFENING AGENT AT LEAST EQUAL IN WEIGHT TO THE WEIGHT OF THE FIBERS THROUGH A THIN RELATIVELY OPEN FIBROUS FABRIC, SAID SHEET COMPRISING A LAYER OF FIBERS WITH SAID PARTICLES DISTRIBUTED THERETHROUGH AND WITH FIBERS OF SAID LAYER INTERSPERSED WITH FIBERS OF SAID FABRIC TO HOLD SAID FABRIC AND LAYER TOGETHER AS A SHEET AND REMOVING A MAJOR PROPORTION OF THE WATER CONTENT OF SAID SHEET, THE IMPROVEMENT COMPRISING COATING THE FABRIC-COVERED SURFACE OF SAID SHEET WITH AN AQUEOUS LATEX OF AN ORGANIC SOLVENT SOLUBLE THERMOPLASTIC MATERIAL, SAID LATEX EXTENDING INTO SAID LAYER TO AN EXTENT LESS THAN ONE-HALF THE THICKNESS OF SAID LAYER, EVAPORATING WATER FROM THE APPLIED COATING AND THEREAFTER SUBJECTING THE DRIED COATING ON SAID FABRIC TO RADIANT HEAT TO FUSE THE DEPOSITED THERMOPLASTIC MATERIAL TO AN ORGANIC SOLVENT PERMEABLE PELLICLE REINFORCING THE UNION BETWEEN SAID FABRIC AND SAID FIBER LAYER. 